Tube reducing machine



Jan. 5, 1965 E. D. DILLING 3,164,043

TUBE REDUCING MACHINE Filed Dec. 7, 1961 2 Sheets-Sheet 1 FIG.1

INVENTOR. Elmer D. Dilling Y Agent Jan. 5, 1965 E. D. DILLING 3,164,043

TUBE REDUCING MACHINE Filed Dec 7, 1961 2 Sheets-Sheet 2 INV EN TOR.

Elmer D. Dilling BY Agent United States Patent 3,l64,tl43 TUBE REDUCING MACHINE liner D. Billing, Las Vegas, Nev., assignor to Titanium Metals Corporation of America, New York, N.Y., a corporation of ll elaware Filed Dec. '7, 1951, Ser. No. 157,745 6 flaims. (til. 8(1i) This invention relates to a machine for manufacturing tubing and more particularly to a machine for reducing the wall thickness or internal diameter of tubing or simultaneously reducing the internal diameter and wall thickness thereof.

Conventional tube reducing machines for production of metallic tubing often operate by a swaging action on a starting tube or blank between rolls or dies which rotate or oscillate in a path of travel parallel to the longitudinal axis of the tube. The dies or rolls are grooved to work down the outer diameter of the initial tube. A long tapered mandrel may be used for internal diameter reduction and a series of dies having grooves of appropriate size and curvature are required for producing tubes of desired outside diameter. Such equipment is expensive, heavy and cumbersome and has often failed to produce tubing of desired accuracy of dimension and surface finish.

It is therefore a principal object of this invention to provide an improved tube reducing machine. Another object of this invention is to provide an improved machine capable of reducing the internal diameter of tubing or reducing the wall thickness thereof, or simultaneously reducing internal diameter and wall thickness. A further object of this invention is to provide a tube reducing machine in which the principles of plastic deformation produced by means of a circular working element causing flow in a direction at a right angle to the direction of travel of the circular working element are employed to reduce internal diameter or wall thickness thereof or both internal diameter and wall thickness simultaneously. A still further object of this invention is to provide a tube reducing machine capable of reducing the internal diameter of a tube and equipped with a tool capable of being adjusted to produce a variety of outside diameters of such tube. These and other objects of this invention will be apparent from the following description thereof and from the annexed drawings in which:

FIG. 1 shows a general side view, partially broken out, illustrating a tube reducing machine embodying features of this invention. I

FIG. 2 shows an end view of the tool or working head used in the machine of FIG. 1 somewhat enlarged.

FIG. 3 shows a section of the tool of FIG. 2 taken along the line 33. I

FIG. 4 shows a sectional and enlarged side view of the working rings of the tool of FIGS. 2 and 3 together with a mandrel designed to produce internal diameter reduction in the tube being reduced.

Referring now to FIG. 1, the machine comprises an elongated heavy frame which is supported by pillars 12 and 14 on blocks 16 and 1%. The top of frame it is provided with horizontal ways 29 on which travel a pair of movable dollies 22 and 24. A central member 26 is provided as part of frame 10 to which are anchored as at 2% the ends of an opposed pair of hydraulic cylinders 30 and 32. The outer ends of the piston rods 34 of hydraulic cylinders 30 and 32 carry rotatable sprockets 35 in whose teeth are engaged the links of chains 38. An upper portion of one of chains 38 is connected to dolly 22 as by heavy bolt 49; the upper end of the other chain 38 being similarly connected to dolly 24 as by bolt 42. The lower ends of chains 38 are anchored to a lower member of frame it) as at 44. Chains 38 are in effect ihdfiiii Patented Jan. 5, 1%65 "ice endless being also carried around inner sprockets 46 which are maintained in fixed, spaced relation to sprockets 36 by bars 48. The axles of sprockets 36 and 46 are supported in a generally horizontal plane by being rotatably mounted on tracks 50.

Mounted on an upper portion of frame 10 and over ways 20 is bearing member 52 which rotatably supports hollow shaft 54. Tool 56, which will hereinafter be described in more detail, is attached as by bolts 57 to one end of shaft 54, and to the other end of shaft 54 is attached bevel gear 5%. Meshing with bevel gear 58 is pinion geared which is in turn fixedly mounted on the shaft 62 of electric motor 64.

Securely mounted on dollies 22 and 24 are grip members 66 and 68 respectively. These grip members may be of conventional jamming wedge design, grip member as being adapted to grip a workpiece tube 70 being fed into the tool 56, and grip member 66 being adapted to grip a finished tube '72 which constitutes the workpiece tube 7%) after passage through and working by tool 56.

Tool 56 is provided with a plurality of working elements in axiallyspaced relationship, as will be apparent from a more complete description of this element included hereinafter. Workpiece tubeitl, during working by tool 56, passes over a mandrel 74 of specific stepped design when reduction of its internal diameter is desired. During working of workpiece tube 7t over mandrel '74, a considerable amount of heat is generated and efiicient working action depends at least in part in maintaining a substantially uniform and proper temperature in the portion of the workpiece tube being worked by the tool 56. This is accomplished by provision in mandrel 74 of a pair of openings shown at 76, as will be more clearly seen in FIG. 4, which are in communication with bore '78 to form a longitudinal passage. Bore 78 at its other end communicates with pipe 8% which is threaded into an end of mandrel '74 as at 82. Pipe 8% supplies a circulating fiuid, preferably a lubricating fluid such as oil. Pipe 8% is connected by swivel joint 34 and union $5 to pipe 36 which leads to circulating pump 88, oil being available in reservoir trough to be circulated by pump 83 through pipes 86 and 8t), mandrel bore 73 and out of openings 76. Valve 91 is interposed in pipe as to control the flow of oil and thermometer 92- is arranged to indicate the temperature of the circulated oil. Electric immersion type heater 94 is placed in trough t) as shown so that the temperature of circulating oil may be raised initially and afterwards maintained at an elevated temperature. It will be apparent that oil flowing out of openings '76 to the area adjacent the working site and will flow along the inside of tubing '72 and eventually out of the end thereof at 95 from where it will flow down into reservoir trough 9%. An additional oil circulating pipe 96 is provided, connected to pipe 86, to supply oil to the outside of workpiece tube 76 at the area where it is being worked by tool 56. This assists in maintaining the workpiece and the working elements of tool as at the desired temperature and at the same time provides lubrication for the working action.

The acton of hydraulic cylinder 3%, which comprises the means for applying tension toan end of workpiece tube 74F to draw it through tool 56, is arranged by provision of four-way valve 97 which controls the directional flow of hydraulic fluid, such as oil, from reservoir 93 pumped under pressure by pump Mil selectively through pipes 1&2 and 1M which is equipped with gauge 106, or through pipe 138, to either end of cylinder 3%. Drain line 119 is provided so that when valve 97" is directing oil into either pipe 14M or 168, oil from the other end of cylinder 30 may be drained therethroueh into reservoir 98. Thus, cylinder 3%) can, through pressure exerted by chain 38, apply tension to dolly 22 to draw tube 72 through tool 56.

It is particularly desirable, however, when reducing the internal diameter of tubing to provide back-tension, as it is termed, to workpiece tube 7b so that the tube passing through tool 515 is maintained under longitudinal tension over the Working area as Well as under additional tension to draw the tube through the tool 55. Means for accomplishing this in the embodiment illustrated include oil pump 114 which also takes its supply from reservoir 93 and which pumps oil through pipe 116 equipped with valve 117 and gauge 118 to the end nearer tool 56 of cylinder 32. By-pass pipe 126 connects to. pipe 116 and is equipped with ordinary valve 122 and also pressure relief valve 124; whose outlet is connected by pipe 126 back to reservoir 93. Drain pipe 12% connects the other end of cylinder 32 to reservoir Q8 and is provided with valve 12%.

In FIG. 1 valve 7 is shown set for operation with workpiece tube 76 being moved through tool 56 to form tube 72'from right to left in the drawing. Pump 1% pumps oil from reservoir 93 to the right hand end of cylinder 30 through pipes 192 and 1%. Oil from the left hand end of cylinder 36 drains back to reservoir 98 through pipes 168 and 110. The oil pressure exerting tension through the SPIOCnZfllI chain and dolly on tube 72 is indicated on gauge 106. At the same time pump 114 is maintaining oil pressure through pipe 116 in the left hand end of cylinder 32, and with valve 122 open this pressure is regulated by relief valve 124, the outlet from this valve draining back to reservoir @3 through pipe 126. The pressure in pipe 116 and the end of cylinder 32, acting through itspiston rod 34 and its sprocket, chain and dolly, and exerting back-tension on tube blank '75; is indicated on gauge 118. During operation higher pressure is maintained in cylinder 30 (as shown on gauge 1%), than in cylinder 32 (as shown on gauge 118) since cylinder 30 must exert draw tension in addition to overcoming the back-tension exerted by cylinder 32.

When it is desired to return the dollies 22 and 24 from left to right (in the drawing) valve 97 is set to selectively transmit oil from pump 1th) into the left hand end of cylinder 30 through pipe 198, oil from the right hand end of cylinder 36 draining back through pipes 104 and 102; valve 122 closed and oil under pres re from pump 114 is transmitted to the left hand end of cylinder 32 through pipe 116. Drain line 128 may draw oil into the right hand end of cylinder 32 during travel of its piston from right to left and this will drain back into reservoir S t; during reversal of this movement. Cross pipe 133 is connected between pipe 128 and pipe 116 and equipped with valve 132 normally closed and so arranged that if it is necessary to move the dolly 24 from right to left when the machine is not operating, this can be done by opening valves 132, 122 and 12d and closing valves 117 and 12b to route oil from pump 114 to the i right hand end of cylinder 32, oil from the left hand end frame 134 and the eccentricity of these partial bores 136 and 138 is diametrically opposite one to the other Adjustably mounted in bores 136 and 138 are annular inner frames in the form of rings 140 and 142 which are characterized by eccentric bores 144 and 14-6. Annular inner frames 140 and 142 may be rotated inside bores 136 and 138 to adjust their relative positions and when set as desired, may be maintained in such adjustment by locking means such as set screws 1 18 set in from the outer edge of outer frame 134.

Mounted in inner frame bores 144 and 1%,as by a press fit, are bearing assemblies 156 and 152'. Mounted in the inner races of bearings me and 152 are working rings 154 and 156 and these may also be conveniently assen fled to the bearings by a press The inner edges 158 and 154, of working rings 15% and 156 are of blunt cross section partially flattened and adapted to cause plastic deformation of a workpiece against which they are pressed during rotation of tool 56 around such workpiece. As will be seen in the drawings, the internal diameter of rings 154 and 156 is greater than the outside diameter of the workpiece tube 79 so that each of the inner edges 158 and res thereof contact and work the metal of the workpiece tube 713 only over a portion of one side thereof at any one time, the contacted portion progressively moving around the circumference of the workpiece tube 7b as the tool rotates around it.

t will be seen that the working elements, that is rings 154 and 156, are not aligned to act on the workpiece 79 in the same plane but are arranged in side by side relationship. Thus these working elements are spaced longitudinally along the workpiece (and also with respect to mandrel 7'4), and are referred to as axially spaced with respect to each other. It will additionally be understood that in a compact tool design the spacing relationship between the sides of the working elements may be very close, but their inner edges, as 158 and tee of rings 154 and 156, will ordinarily be somewhat further spaced apart.

Flat cover rings 162 are provided to maintain inner frames 14% and 142, bearings 19% and E52, and working rings 15d and 156 in their proper adjusted relationship. These are firmly attached to opposite sides of outer frame 134 by means of bolts 164.

Heavy bolts 57 pass through cover rings 162 and outer frame 134 to fasten the tool ss as an integral assembly fixedly to the end of hollow shaft 54.

Referring now to FIG. 4 the mandrel 74 for producing reduction of internal diameter of a workpiece such as workpiece tube 74 is characterized by being stepped, with shoulders or risers as at 166 and at 168. These shoulders 166 and 168 produce mandrel diameter reduction corresponding to the desired reduction in internal diameter of the workpiece tube It! and are longitudinally spaced along mandrel 74 to correspond with the spacing between working edges 158 and 16% respectively of working rings 154 and 156. Working edges 15% and 1641 continuously work metal of workpiece tube down onto the mandrel steps following shoulders 166 and 163 and by appropriate setting of rings E54 and 156 by their frames 144 and 146 in tool 56, can also effect a reduction in Wall thickness of workpiece tube 7%.

In operation of the machine, the working rings 154 and 156 of tool 56 are first adjusted in their inner frames 14%) and M2 to provide the required reduction in tube outside diameter. A workpiece tube 7% is pointed (by any convenient and known method) and the pointed end passed through tool 56 and gripped by grip 66 on dolly 22. The feed end of workpiece tube '76 is gripped by grip 6% on dolly 24 at any convenient point along its length. A mandrel '74, of design to accomplish the required inside diameter reduction, is threaded onto pipe fill as at 82 and inserted into the workpiece tube 7t so that its shoulders 166 and 168 are aligned with corresponding edges 15? and 161 of Working rings 154 and 156. Connection of pipe 81 with swivel 84 to pipe St? is conveniently made by union 85. Heater 94 is then turned on to heat the oil in reservoir trough and pump 88 is started to circulate hot oil through the mandrel 74; and also to the outside surface of the workpiece tube 7t and working rings 154 and through pipe 96. When the tem ture of these elements has been Sllll'lClfil'lflY raised, as indicated by a circulating oil temperature of preferably between 260 and 360 F, motor 64 is started to rotate tool 56 around the workpiece tube '78. Pump 1% is started to actuate hydraulic cylinder 3% to draw the finished tube 72 through tool 55 and pump 114 is operated and relief valve 124 set to maintain back-tension on the workpiece tube iii. The set-ting of the hydraulic system valves during operation is as shown in FIG. 1 of the drawings and as previously described. During operation the circulating oil is maintained at elevated temperature by adjustment of heater M and valve 91.

As the workpiece tube 70 is drawn through the tool 56 the working rings 15 i and 156 progressively work the metal of the workpiece tube 7% by plastic deformation causing flow in a direction at a right angle to the direction of travel or working rings 15 and 15b. The working action produces a reduced tube '72 corresponding in internal diameter to the diameter of the small end of the mandrel 7d and of wall thickness determined by the spacing between the edge 153 of working ring 154 and the outside suriace of the small end of the mandrel '74 aligned with it.

After reduction of workpiece tube 7'3 over its length (except for a necessary gripping portion at each end) tool 56 is stopped, oil circulating pump 33 is shut down, hydraulic system pumps 1% and 114 are shut down, mandrel 4 is removed by separating pipe and swivel 41 from pipe 86 at union 35, and the ends of the workpiece tube 7%) and finished tube 72 are removed respectively from grips 68 and Finished tube 72 is then withdrawn through tool 56; and may be further processed by separation of point and workpiece stub ends and any further finishing desired. The dollies 22 and 2dare then repositioned and the operation is repeated to reduce another length of tube.

The speed of tool 5s rotation and the settings to produce draw and back-tension and other operating factors, will necessarily be adjusted with regard to the size of the tubing, the degree of reduction accomplished and the tubing material. As an example, a workpiece tube 76 of commercially pure titanium tubing of 1.25 inches outside diameter and 1.0. inches inside diameter was reduced to produce a tube of 0.920 inch outside diameter and 6.780 inch inside diameter. A machine of the type illustrated in FIG. 1 was used with the tool ss rotated at 550 rpm. and the circulat ng oil maintained at a uniform temperature of about 200 F. Reli f valve 124 was set to show a pressure on gauge 318 of 50 p.s.i. which produced a back-tension calculated from previous oalibra tion of 6,100 psi. over the workpiece tube wall section area, while cylinder it) was pulling the tube through the rotating tool 56 at a draw speed of 6 inches of workpiece feed tube length per minute, a pressure of 85 psi. showing on gauge 1%.

Control of the temperature of mandrel 7 appears to be important for efi-lcient production of good finish tubing. The working action of rings 154 and 156 on workpiece tube Til produces a considerable amount of heat and as the reduction proceeds along a length of workpiece tube the mandrel and the workpiece will become subiect to local overheating unless provisions for circulating oil, or other iluid, as ,hereinbefore described. Should the mandrel, and more particularly of course, the workpiece tube in contact with it, become overheated the workpiece tube will become susceptible to fracture under the working rings d and 156 due largely to the tension applied to the tube over the working area. On the other hand, at the beginning of an operation with the mandrel cold, excessive work hardening of the workpiece tube can cause embrittlement resulting in cracks in the workpiece and sometimes fracture. For these reasons at the start of a tube reducing operation it is advantageous to heat the the workpiece tube 76 quickly'up to a desirable operating temperature, and after the operaton has been running, to shut off or cut down the current to the heater and circulate the oil to prevent overheating but still maintaining it at an elevated temperature. it has been found advantageous to maintain the circulating oil at a substantially uniform elevated temperature, and this may be up to sevoil circulated to mandrel 74 to bring it and eral hundred degrees Fahrenheit. When reducing titanium tubing, for example, an oil temperature of between 200 F. and 300 F. has been found to provide good operating conditions. If necessary or desirable, conventional cooling coils, circulating water, may be employed in the oil circulating system, but ordinarily adequate control of flow and temperature may be obtained by valve 91 and heater 94.

Provision of the swivel joint 84 between pipes and 36 to allow pipe 86 to freely rotate, is important to produce tubing with superior inside surface finish. As the machine operates tool 5'6 is revolved around workpiece tube 70, but this workpiece tube 7% and the reduced tubing 72 does not rotate but simply travels through tool 56 with its length increased corresponding to the reduction performed. Mandrel '74 stays in the same longitudinal position relative to working rings 15 i and 156 but amazingly, and for reasons not completely understood, tends to rotate in a direction opposite to the direction of rotation of tool 56. This tendency for mandrel 74 to rotate is apparently very strong, and if mandrel '74 is fixedly mounted and restrained, the internal surface of workpiece tube 70 can become scuifed or rough. However, when mandrel '74 is connected as described and shown, being substantially floating and freely rotatable in tube 7%), its tendency to rotate is uninhibited and it will in fact rotate continuously, but as explained above in adirection opposite to that of tool 56. It has been found, however, that when themandrel is allowed to freely rotate, sliding or scuffing of the internal sufacc of the workpiece 7% on the surface of mandrel '74 is eliminated and a smooth, even, internal surface finish results.

it is significant that the machine of this invention produces internal diameter reduction alone or combined with wall thickness reduction by a process in which the metal working elements travel around their axes which are generally parallel to the longitudinal axis of the tube. The principle involved is therefore not one of rolling in the generally accepted sense, or of swaging, but results in metal working and flow in a direction principally at right angles to the path of travel of the tool working edge. As the rings 154 and 156 travel around the workpiece, metal is displaced laterally out from under their working edges.

Provision of means for applying back-tension to the workpiece tube is particularly important during reduction of inside diameter of tubing and it is also useful to produce improved operation during reduction of wall thickness. When reducing inside diameter or wall thickness there appears to be some tendency for metal to pile up somewhat ahead of the working rings as they travel around the workpiece and to form a ridge between the working areas. Application of back-tension under these conditions relieves this tendency and the metal flows smoothly out at lengthwise of the tube and right angles to the diameter plane of the working rings. It is interesting that backtension which is applied longitudinally along the tube length, effectively reduces or stops metal tending to flow or pile up ahead of the working rings in a direction at right angles to the length of the tube and of course, the direction of application of the back tension. The backtension should be maintained during operation at not more than about 50% of the yield strength of the material of which the workpiece is constituted, the yield strength being determined at room temperature by conventional and known methods. The pressure shown on pressure gauge 118, as will be apparent, is applied as a force over the area of the piston head in cylinder '32 and can be calculated to indicate the back tension in pounds per square inch applied to the original cross sectional area of the wall of the workpiece 70; Alternatively the gauge may be calibrated for the same purpose by arranging a strain gauge applied to a workpiece tube '70 and plotting tension forces actually obtained for various gauge pressures.

The machine of this inventionis useful for reducing welded tubing. The welded area will be found'to be worked down by the action of tool 56 so that a uniform wall thickness tube is produced as a product. In fact if the machine is set to produce a substantial reduction in wall thickness, area or sink, it is sometimes difficult, after reduction, to recognize the previously welded seam.

A variety of sizes of tubing using a range of workpiece tube sizes may be produced by the machine of this invention. The working rings of tool 56 may be adjusted as described within limits to provide the desired outside diameter of the finished tubing, with the individual working rings set to produce the desired reduction effect. The mandrel must be designed for the specific internal diameter reduction desired except in the case where wall reduction only is accomplished, in which case the mandrel will be a uniform cylindrical piece. When arranging the mandrel for internal diameter reduction it is advantageous to-provide steps that will accomplish about one half the total reduction under each working ring with the diameter of the mandrel at its small end being the size desired as the internal diameter of the reduced tube. The angle of the shoulders between steps is preferably from 10 to 40 degrees to the longitudinal axis of the mandrel and the nose or working edge of the corresponding working ring should generally conform to the configuration of the mandrel as it reduces over the shoulder and down to the following smaller diameter step.

The machine of this invention has been found to produce a useful degree of correction of eccentricity in the workpiece tube. The reason for this is not precisely known but it is postulated that the axially spaced working rings working over the mandrel, which is essentially floating in the workpiece tube, tend to work out the metal to produce a uniform wall thickness in the finished tube. Since the mandrel and workpiece floats between the working rings, the forces exerted by the individual working rings are essentially equal. It is significant that reductions of wall thickness up to 65% can be obtained simultaneously with reduction in internal diameter (sink), and at the same time an improvement in concentricity can be imparted to the tube.

This application is a continuation-in-part of my copending application Serial No. 78,469, filed December 27, 1960.

I claim:

1. A tube reducing machine comprising:

(a) a frame,

(b) a tool rotatably mounted on said frame, said tool having a plurality of circular working elements in axialy spaced relationship and with their axes parallel to the axis of a metal workpiece tube passing therethrough,

() means for rotating said tool around said metal workpiece tube,

(d) a stepped mandrel having a plurality of shoulders disposed inside said workpiece tube, and

(e) means for applying tension to an end of said workpiece tube to draw it through said tool,

each of said shoulders of said mandrel being aligned with one of the working elements of said tool, an edge of each of said working elements being adapted to cause plastic deformation of the metal of said workpiece tube onto a step of said mandrel and following the'shoulder of said mandrel with which each is aligned, to produce reduction of the internal diameter of said work iece tubing.

2. A tube reducing machine comprising:

(a) a frame,

(b) a tool rotatably mounted on said frame, said tool having a plurality of working rings in side by side relationship and with their axes parallel to the axis of a metal workpiece tube passing therethro'ugn,

(0) means for rotating said tool around said metal workpiece tube, V

(d) a stepped mandrel having a plurality of shoulders disposed inside said workpiece tube, and

(e) means for applying tension to an end of said workpiece tube to draw it through said tool, each of said shoulders of said mandrel being aligned with the inner edge of one of said working rings of said tool. the said edge of each of said working rings being adapted to cause plastic deformation of the metal of said workpiece tube onto a step of said mandrel and following the shoulder of said mandrel with which each is aligned, to produce reduction of the internal diameter of said workpiece tubing.

3, A tube reducing machine comprising:

(a) a frame,

(11) a tool rotatably mounted on said frame, said tool having a pair of working rings in side by side relationship and with their axes parallel to the axis of a metal workpiece tube passing therethrough,

(c) means for rotating said tool around said metal workpiece tube,

(d) a stepped mandrel having a pair of shoulders disposed inside said workpiece tube, and

(6) means for applying tension to an end of said workpiece tube to draw it through said tool,

each of said shoulders of said mandrel being aligned with the inner edge of one of said working rings of said tool, the said edge of each of said working rings being adapted to cause plastic deformation of the metal of said workpiece tube onto a step of said mandrel and following the shoulder of said mandrel with which each is aligned, to produce reduction of the internal diameter of said workpiece tubing.

4. A tube reducing machine comprising:

(a) a frame,

(b) a tool rotatably mounted on said frame, said tool having a plurality of Working rings in side by side relationship and with their axes parallel to the axis of a metal workpiece tube passing thcrethrough,

(0) means for rotating said tool around said metal workpiece tube,

(0') a mandrel disposed within said workpiece tube and aligned with said working rings of said tool,

(6) means for applying tension to one end of said workpiece tube to draw it through said tool, and

(1) means for applying back tension to the other end of said workpiece tube,

the inner edges of said working rings being adapted to cause plastic deformation of th metal of said workpiece tube and displacement thereof in a direction at a right angle to the direction of travel of said working rings around the circumference of said metal workpiece tube.

5. A tube reducing machine comprisin (a) a frame, u

(b) a tool rotatably mounted on said frame, said tool having a pair of working rings in side by side relationship and with their axes parallel to the axis of a metal workpiece tube passing thcrethrcugh,

(0) means for rotating said tool around said metal workpiece tube,

(d) a mandrel disposed within said workpiece tube and aligned with said working rings of said tool,

(e) means for applying tension to one end of said workpiece tube to draw it through said tool, and

(f) means for applying back tension to the other end of said workpiece tube,

the inner edges of said working rings being adapted to cause plastic deformation of the metal of said workpiece tube and displacement thereof in a direction at a right angle to the direction of travel of said working rings around the circumference of said metal workpiece tube. 6. A tube reducing machine comprisii a frame, a tool rotatably mounted on said frame, said tool having a plurality of working rings in side by side relationship and with their axes parallel to the a of a metal workpiece tube passing therethrough, means for rotating said tool around said metal workpiece tube, a mandrel disposed within said workpiece tube and aligned with said working rings of said tool, and means for applying tension to one end of said workpiece tube to draw it through said tool, the inner edges of said working rings being adapted to cause plastic deformation of the metal of said workpiece tube and displacement thereof in a direction at a right angle to the direction of travel of said Working rings around the circumference of said metal workpiece tube.

References Cited in the file of this patent UNITED STATES PATENTS ODonnell Sept. 15, 1903 Coryell Feb. 27, 1927 Cushwa Mar. 3, 1936 Inscho Feb. 22, 1938 Findlater Apr. 8, 1941 Curtis Sept. 12, 1950 Le Fiell July 3, 1962 

1. A TUBE REDUCING MACHINE COMPRISING: (A) A FRAME, (B) A TOOL ROTATABLY MOUNTED ON SAID FRAME, SAID TOOL HAVING A PLURALITY OF CIRCULAR WORKING ELEMENTS IN AXIALLY SPACED RELATIONSHIP AND WITH THEIR AXES PARALLEL TO THE AXIS OF A METAL WORKPIECE TUBE PASSING THERETHROUGH, (C) MEANS FOR ROTATING SAID TOOL AROUND SAID METAL WORKPIECE TUBE, (D) A STEPPED MANDREL HAVING A PLURALITY OF SHOULDERS DISPOSED INSIDE SAID WORKPIECE TUBE, AND (E) MEANS FOR APPLYING TENSION TO AN END OF SAID WORKPIECE TUBE TO DRAW IT THROUGH SAID TOOL, EACH OF SAID SHOULDERS OF SAID MANDREL BEING ALIGNED WITH ONE OF THE WORKING ELEMENTS OF SAID TOOL, AN EDGE OF EACH OF SAID WORKING ELEMENTS BEING ADAPTED TO CAUSE PLASTIC DEFORMATION OF THE METAL OF SAID WORKPIECE TUBE ONTO A STEP OF SAID MANDREL AND FOLLOWING THE SHOULDER OF SAID MANDREL WITH WHICH EACH IS ALIGNED, TO PRODUCE REDUCTION OF THE INTERNAL DIAMETER OF SAID WORKPIECT TUBING. 